The present invention relates generally to cardiac leads. More particularly, the present invention pertains to a cardiac lead system having multiple leads.
Electrodes implanted in or about the heart have been used to reverse (i.e., defibrillate or cardiovert) certain life threatening arrhythmias by applying electrical energy through the electrodes to return the heart to a normal rhythm. Electrodes have also been used to sense and deliver pacing pulses to the atrium and ventricle. The electrode in the atrium senses the electrical signals that trigger the heartbeat. The electrode detects abnormally slow (bradycardia) or abnormally fast (tachycardia) heartbeats. In response to the sensed bradycardia or tachycardia condition, a pulse generator produces pulses or signals to correct the condition. The same node used to sense the condition is also used in the process of delivering a corrective pulse or signal from the pulse generator of the pacemaker.
There are four main types of pulses which are delivered by a pulse generator. Two of the signals or pulses are for pacing the heart. First of all, there is a pulse for pacing the heart when it is beating too slowly, and the pulse triggers the heart beat. The pulses are delivered at a rate to increase the heart rate to a desired level. The second type of pacing, called antitachycardia pacing, is used on a heart that is beating too fast. In antitachycardia pacing, the pacing pulses are delivered initially at a rate faster than the beating heart. The rate of the pulses is then slowed until the heart rate is at a desired level. The third and fourth type of pulses are used when the heart is beating too fast and the heart is fibrillating. The third type is called cardioversion. This is delivery of a relatively low energy shock, typically in the range of 0.75 to 1 joule, to the heart. The fourth type of pulse or signal is a defibrillation signal which is the delivery of a high energy shock, typically up to 34 joules, to the heart.
Sick sinus syndrome and symptomatic AV block constitute the major reasons for insertion of cardiac pacemakers today. Cardiac pacing may be performed by the transvenous method or by electrodes implanted directly onto the epicardium, where transvenous pacing may be temporary or permanent. In temporary transvenous pacing, an electrode lead is introduced into a peripheral vein and fluoroscopically positioned against the endocardium. The external terminals of the leads are connected to an external cardiac pacemaker which has an adjustable rate and milliamperage control. Temporary transvenous pacing is utilized prior to insertion of a permanent pacing system and in situations in which the indication for pacing is judged to be reversible (drug-induced AV block or bradycardia) or possibly irreversible and progressive (AV and bundle branch blocks associated with myocardial infarction).
Permanent transvenous pacing systems are implanted under sterile surgical conditions. An electrode lead is generally positioned in the right ventricle and/or in the right atrium through a subclavian vein, and the proximal electrode terminals are attached to a pacemaker which is implanted subcutaneously. Some patients require a pacing system to correct an abnormally slow heart (bradycardia condition) as well as a defibrillation system to detect when the heart starts beating abnormally fast (tachycardia condition) and to defibrillate or deliver a pulse to the heart to correct the abnormally fast heartbeat. In the past, a common practice for a patient having both of these conditions would be to provide two different leads attached to the heart. One would be implanted for delivering pacing signals to the heart to correct for the bradycardia condition. A separate lead would be implanted to sense a fast beating heart and defibrillate the heart to correct for the tachycardia condition. One lead is placed in the atrium and the other lead is placed in the ventricle.
Having two separate leads implanted within the heart is undesirable for many reasons. Among the many reasons is that the implantation procedure for implanting two leads is more complex and also takes a longer time when compared to the complexity and time needed to implant a single lead. In addition, two leads may interact with one another after implantation or in vivo which can result in dislodgment of one or both of the leads. In vivo interaction may also cause abrasion of the insulative layer along the lead which can result in an electrical failure of one or both of the leads. Another problem is that as more leads are implanted in the heart, it can become increasingly difficult to add additional leads. Two separate leads also increase the risk of infection and may result in additional health care costs associated with implantation and follow-up. Thus, there is a need for a lead which allows for both energy delivery to and sensing from both atrial locations and ventricular locations while reducing the detrimental interactions between the leads that perform these functions.
A single-pass endocardial lead is provided which is adapted for implantation on or about the heart and is adapted for connection to a system for monitoring or stimulating cardiac activity and includes a lead body. In one embodiment, the lead includes a main lead and a transverse lead, where the both leads have at least one electrode each. The transverse lead extends laterally from the main lead at a point which is between the distal and proximal ends of the main lead and curves around the longitudinal axis of the main lead to partially encircle at least a portion of the main lead. In an additional embodiment, there is provided a lead system which includes a first lead and a second lead. Both the first and the second lead include at least one electrode, and the second lead further includes a sleeve through which the first lead is adapted to move so as to attach the first lead to the second lead. These lead structures allows for both electrical energy pulses to be delivered to and cardiac signal to be sensed from both atrial locations and ventricular locations while reducing the detrimental interactions between the leads that perform these functions.
In one embodiment, the lead comprises the main lead and the transverse lead. The main lead includes a main lead body with a longitudinal axis and at least one electrode, where the main lead body extends from a proximal end to a distal end and is adapted to carry signals to and from the heart. The transverse lead includes a transverse lead body and at least one electrode, where the transverse lead body is also adapted to carry signals to and from the heart. The transverse lead body extends laterally from the main lead body between the proximal end and the distal end and curves around the longitudinal axis to partially encircle at least a portion of the main lead. In one embodiment, the transverse lead is adapted to press the at least one electrode on the transverse lead against endocardial tissue.
In one embodiment, the main lead and the transverse lead are adapted to be implanted into the heart, where the proximal end of the main lead is releasably coupled to an implantable pulse generator to allow for cardiac signals to be sensed from the heart and for energy pulses to be delivered to the heart through the electrodes positioned on the main lead and the transverse lead. In one embodiment, the main lead is implanted with its distal end positioned in the right ventricle and the transverse lead positioned in the right atrium. Alternatively, the main lead is implanted with its distal end positioned in the right ventricle or right atrium and the transverse lead positioned in at least partially within the coronary sinus vein with its electrodes adjacent the left atrium and or the left ventricle.
In one embodiment, at least a portion of the main lead and at least a portion of the transverse lead are both adapted to be housed within an implant catheter. After inserting the implant catheter containing at least a portion of the main lead and the transverse lead, the main lead and the transverse lead are passed through the catheter. Use of the implant catheter to deliver the main and transverse leads allows for greater ease in implanting the lead as compared to not using the catheter.
In an alternative embodiment, the lead system comprises a first lead and a second lead. The first lead includes a lead body and at least one electrode, and the second lead includes at least one electrode and a sleeve, where the first lead is adapted to move through the sleeve to attach the first lead to the second lead. Both the first lead and the second lead are adapted to sense cardiac signals from and deliver electrical pulses to a heart. In one embodiment, the sleeve is coupled to the external surface of the second lead body. In alternative embodiment, the sleeve is an integral part of (i.e., formed with) the second lead body.
In one embodiment, the sleeve is a tubular segment having an inner surface defining an opening adapted to receive and pass at least a portion of the lead body of the first lead. In one embodiment, the sleeve on the second lead is passed over at least a portion of the first lead. The first lead is then inserted, or implanted, into a heart. The second lead is then inserted into the heart by passing the sleeve over at least a portion of the inserted first lead. In one embodiment, a guidewire is first inserted into the heart. The first lead is then advanced over the guidewire to position the first lead in the heart, where the first lead has a lumen which extends between a distal end and a proximal end. Alternatively, the lumen of the first lead extends only partially through the lead body of the first lead near or at the distal end to allow for an over-the-wire insertion of the first lead.
The sleeve is then passed over at least a portion of the inserted first lead to insert the second lead into the heart. In one embodiment, a stylet is used to advance the second lead into the heart. The proximal ends of the leads are then held and the stylet and guidewire withdrawn. The leads are then connected to the implantable pulse generator for use in the patient.
These and other embodiments, aspects, advantages, and features of the present invention will be set forth in part in the description which follows, and in part will become apparent to those skilled in the art by reference to the following description of the invention and referenced drawings or by practice of the invention. The aspects, advantages, and features of the invention are realized and attained by means of the instrumentalities, procedures, and combinations particularly pointed out in the appended claims.